AD5940 Temperature Example

Question

I'm having trouble with the AD5940 temperature example. No results were printed until I powered the SINC2NOTCH block by modifying this line 
 
 AD5940_AFECtrlS(AFECTRL_TEMPCNV|AFECTRL_ADCCNV|AFECTRL_SINC2NOTCH, bTRUE); /* Start ADC convert */ 
 The code now prints four nonsensical results and stops: 
 Hello AD5940-Build Time:13:08:26 Internal calibration register value: Gain: 0x00004000 Offset: 0x00000000 Result[0] = -14, -274.30(C) Result[1] = 10178, 561.45(C) Result[2] = 11926, 704.79(C) Result[3] = 12369, 741.12(C) 
 How do I resolve this?

NormS · Accepted Answer

After looking at page 399 of the ADuCM350 hardware reference manual 
 https://www.analog.com/media/en/technical-documentation/user-guides/aducm350_ug-587.pdf 
 I modified the sequence so that the temperature sensor was powered on and off along with the ADC. 
 //generate sequence to measure temperature sensor output
 AD5940_SEQGenInit(buff, BUFF_SIZE); //init sequence generator
 AD5940_SEQGenCtrl(bTRUE); //from now on, record all register operations rather than write them to AD5940 through SPI.
 AD5940_SEQGpioCtrlS(AGPIO_Pin1); //pull high AGPIO1 so we know the sequencer is running by observing pin status with oscilloscope etc.
 AD5940_SEQGenInsert(SEQ_WAIT(16*200)); /* Time for reference settling(if ad5940 is just wake up from hibernate mode) */
 AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_TEMPSPWR, bTRUE); /* Turn ON ADC and temperature sensor power */
 AD5940_SEQGenInsert(SEQ_WAIT(16*50)); /* wait another 50us for ADC to settle. */
 AD5940_AFECtrlS(AFECTRL_TEMPCNV|AFECTRL_ADCCNV|AFECTRL_SINC2NOTCH, bTRUE); /* Start temperature and ADC convert */
 AD5940_SEQGenInsert(SEQ_WAIT(WaitClks));
 AD5940_AFECtrlS(AFECTRL_TEMPCNV|AFECTRL_ADCCNV|AFECTRL_SINC2NOTCH, bFALSE); /* Stop ADC convert, hw ref manual p. 53 says TEMOCNV resets to 0 after conversion */
 AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_TEMPSPWR, bFALSE); /* Turn off ADC and temperature sensor power */
 AD5940_SEQGenInsert(SEQ_WAIT(20)); /* Add some delay before put AD5940 to hibernate, needs some clock to move data to FIFO. */
 AD5940_SEQGpioCtrlS(0); /* pull low AGPIO so we know end of sequence.*/
 AD5940_EnterSleepS();/* Goto hibernate */
 AD5940_SEQGenCtrl(bFALSE); /* stop sequence generator */
 if(AD5940_SEQGenFetchSeq(&pSeqCmd, &seq_len) != AD5940ERR_OK){
 
 I'm now getting reasonable values 
 Gain: 0x00004000 Offset: 0x00000000 Result[0] = 3622, 23.86(C) Result[1] = 3622, 23.86(C) Result[2] = 3623, 23.94(C) Result[3] = 3622, 23.86(C) 
 These increase and decrease as I warm and cool the IC)

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AD5940 Temperature Example